1. Field of Invention
The present invention relates to an active-matrix type electrooptical device, a projection-type display apparatus incorporating the electrooptical device, and a method for manufacturing the electrooptical device. Particularly, the present invention relates to an electrooptical device having a pixel switching thin-film transistor (TFT) in a laminate structure formed on a substrate thereof, a projection-type display apparatus incorporating the electrooptical device as a light valve, and a manufacturing method for manufacturing the electrooptical device.
2. Description of Related Art
Active-matrix type electrooptical devices suffer from a change in TFT characteristics as a result of photocurrent leakage that occurs when incident light enters a channel region of a pixel switching TFT in each pixel. Since an electrooptical device for use as a light valve in a projector uses a high-intensity light ray, blocking the admittance of light into the channel region of the TFT and the peripheral area of the channel region is important. A light shield layer, arranged on a counter substrate, that defines an aperture area of each pixel, or a data line, fabricated of a metal layer such as Al (aluminum) running over the TFT on a TFT array substrate blocks the admittance of light into the channel region or its peripheral area. A light shield layer, fabricated of a refractory metal, for example, is arranged on the TFT array substrate in a position facing the TFT from below. Such a light shield layer arranged beneath the TFT prevents light back-reflected from the TFT array substrate from entering the TFT in the electrooptical device. For example, in an optical system that is composed of a plurality of electrooptical devices combined with a prism, such a light shield layer prevents returning light such as a light ray passing through the prism from another electrooptical device from entering the TFT in one electrooptical device of interest.
For example, such an electrooptical device, having high light-shield performance, can be used as a light valve in a projection-type display apparatus which is subject to high-intensity light.
The above light shield techniques have the following disadvantages. For example, in the technique of using a light shield layer formed on a counter substrate or a TFT array substrate, the light shield layer and the channel region are substantially spaced apart from each other with a liquid-crystal layer, an electrode, and an interlayer insulator that are interposed therebetween. However, the light shield performance for blocking light that is obliquely incident on the area between the light shield layer and the channel region is not sufficient enough. In a compact electrooptical device to use as a light valve in a projector, the incident light is a light beam into which a lens converges light from a light source, and contains a significant component of obliquely incident light (for example, 10% of the incident light is oblique by 10 degrees to 15 degrees with respect to a direction normal to the substrate). Such insufficient light shield performance to the obliquely incident light creates a problem in operation.
Light entering the electrooptical device through an area having no light shield layer may be reflected off the top surface of the substrate, the top surface of the light shield layer formed on the substrate, or the underside of the data line, i.e., the inner surface of the data line facing the channel region. The light reflected in this way may be reflected again off the top surface of the substrate, or the inner surfaces of the light shield layer and the data line, thereby causing multiple reflections. The multiple reflections may reach the channel region of the TFT.
As a demand for display image with higher quality in the electrooptical device increases, the electrooptical device has a higher definition and a finer pixel pitch. Furthermore, as incident light rays intensifies in level to present a brighter image, a variety of conventional light shield techniques become unable to sufficiently block the admittance of light. Stray light causes a change in transistor characteristics of the TFT, resulting in flickering and leading to degradation of the display image quality.
Expanding the formation area of the light shield layer has been contemplated to increase light tightness. Expanding the formation area of the light shield layer makes it difficult to increase the aperture ratio of each pixel. It is noted that the aperture ratio needs to be increased for a brighter display image. The light shield layer beneath the TFT and the light shield layer (ex. a data line) over the TFT result in internal reflections and multiple reflections of obliquely incident light rays. The expanding of the formation area of the light shield layer increases internal reflections and multiple reflections of light and thus causes problems.
In view of at least the above problems, the present invention has been developed. It is an object of the present invention to provide an electrooptical device which features high light tightness, and presents a bright and high-quality image, a projection-type display apparatus incorporating the electrooptical device, and a method for manufacturing the electrooptical device.
To resolve the above problems, a first electrooptical device of the present invention includes a first substrate, a pixel electrode arranged above the first substrate, a thin-film transistor arranged above the first substrate and connected to the pixel electrode, and a first light shield layer arranged over the gate electrode of the thin-film transistor formed over and facing the channel region of the thin-film transistor with a gate insulator interposed therebetween, wherein the first light shield layer is formed, laterally surrounding the channel region as a light shield side wall.
In accordance with the first electrooptical device of the present invention, the first light shield layer deposited above the channel region of the TFT prevents light coming in from the top side of the first substrate from entering the channel region. The first light shield layer, laterally surrounding the channel region as the light shield side wall, prevents light from entering obliquely or laterally into the channel region. Since the present invention prevents light coming in from the top side of the first substrate from entering the channel region of the TFT, the electrooptical device is free from erratic operations of the TFT and a drop in reliability of the TFT.
In one embodiment, the first electrooptical device of the present invention can include a second substrate opposed to the first substrate, and an electrooptical material interposed between the first substrate and the second substrate. This embodiment presents a light-tight electrooptical device, such as a liquid crystal device, having the electrooptical material interposed between a pair of the substrates.
In another embodiment of the first electrooptical device of the present invention, a matrix of the pixel electrodes and the thin-film transistors can be arranged on the first substrate. In accordance with this embodiment, an active-matrix type electrooptical device such as a liquid crystal device having high light tightness can be achieved.
In another embodiment of the first electrooptical device of the present invention, the light shield side wall can be formed of the first light shield layer formed in a light shield side wall formation trench formed in an insulator below the first light shield layer.
The first electrooptical device having the above construction can be manufactured using the following method. Specifically, a method for manufacturing an electrooptical device including a first substrate, a pixel electrode arranged above the first substrate, and a TFT arranged above the first substrate and connected to the pixel electrode, includes forming, above the first substrate, the TFT including a channel region, a gate insulator formed on the channel region, and a gate electrode on the gate insulator, with the gate electrode facing the channel region with the gate insulator interposed therebetween. The method can further include depositing at least one interlayer insulator covering the TFT subsequent to the formation of the TFT, forming, in the interlayer insulator, a side wall formation trench that runs by the side of the channel region of the TFT, and depositing a first light shield layer covering at least the channel region of the TFT, wherein the first light shield layer is also deposited in the side wall formation trench as a light shield side wall when the first light shield layer is formed.
In another embodiment of the first electrooptical device of the present invention, a drain electrode, formed over a drain region of the TFT, is electrically connected to the drain region of the TFT, the pixel electrode, formed over a drain electrode, is electrically connected to the drain electrode, and the drain electrode is fabricated of a conductive layer having a light shield property formed over and covering the channel region. In this embodiment, besides the first light shield layer, the drain electrode having a light shield property blocks light, thereby reliably preventing light from entering the channel region.
In this embodiment, it is preferable that the drain electrode and the first light shield layer form a storage capacitor with an insulator, as a dielectric layer, interposed between the drain electrode and the first light shield layer preferably form a storage capacitor. In this arrangement, each of the drain electrode and the first light shield layer is wide enough to cover the channel region. By using the insulator interposed therebetween as a dielectric layer, a storage capacitor is formed. This arrangement eliminates the need for routing a capacitive line to each pixel, thereby increasing the aperture ratio of each pixel.
In another embodiment of the first electrooptical device of this invention, a data line formed over the source region of the TFT is electrically connected to a source region of the TFT. Also, the data line is fabricated of a conductive layer having a light shield property and covering the channel region from above. In this embodiment, beside the first light shield layer, the data line having a light shield property blocks light, thereby preventing light from entering the channel region. In this embodiment, an active layer of the TFT is preferably formed of a semiconductor layer that is arranged beneath the data line and within the formation area of the data line.
In this arrangement, the data line having a light shield property blocks light to the entire semiconductor layer forming the TFT, and the TFT is formed within the formation area of the data line. The pixel aperture ratio is thus increased. In this case, the data line extends in a line having an equal line width.
In another embodiment of the first electrooptical device of the present invention, a second light shield layer is laminated below the channel region. Light, which is reflected off the first substrate or is reflected outside the first substrate and enters again the first substrate from behind, is blocked by the second light shield layer in this arrangement. The electrooptical device is free from erratic operations of the TFT and a drop in reliability of the TFT, which can be caused when the reflected light enters the channel region of the TFT.
In this embodiment, preferably, the first light shield layer is routed through the side wall formation trench and is electrically connected to the second light shield layer.
Since the channel region of the TFT is entirely laterally surrounded by the first light shield layer, the light shield side wall, and the second light shield layer in this arrangement, light coming in from any direction is reliably blocked. Since the first light shield layer and the second light shield layer are electrically connected to each other, fixing the second light shield layer to a potential automatically fixes the first light shield layer to the same potential. The first light shield layer is easily used as a fixed-potential capacitive electrode of a storage capacitor.
In this case, the first light shield layer may be directly connected to the second light shield layer, or may be connected to the second light shield layer through another conductive layer having a light shield property. When the first light shield layer is connected to the second light shield layer through another conductive layer having a light shield property, a conductive layer, fabricated of the same material as the conductive layer forming the gate electrode, may be deposited on the bottom of the side wall formation trench, and the light shield side wall may be formed on the conductive layer.
In the manufacturing of the first electrooptical device, a second light shield layer, an underlayer insulator, a semiconductor layer forming the thin-film transistor, and a gate insulator of the thin-film transistor are deposited on the surface of the first substrate, prior to formation of the thin-film transistor on the top side of the first substrate. After forming a connection trench in the gate insulator and the underlayer insulator, running by the side of the channel region of the thin-film transistor and reaching the second light shield layer, a conductive layer, which forms the gate electrode, is also deposited in the connection trench when the gate electrode is produced. The interlayer insulator is deposited on the gate electrode, and then, the side wall formation trench is formed, communicating and being integral with the connection trench when the side wall formation trench is formed. Subsequently, the first light shield layer is deposited, and when the first light shield layer is deposited, the first light shield layer also be formed in the side wall formation trench to form the light shield side wall connected to the conductive layer in the side wall formation trench.
When the first light shield layer is directly connected to the second light shield layer, the first light shield layer may be formed in the side wall formation trench reaching the bottom thereof.
In manufacturing the electrooptical device in this arrangement, a second light shield layer, an underlayer insulator, a semiconductor layer forming the thin-film transistor, a gate insulator of the thin-film transistor, and a gate electrode of the thin-film transistor are deposited on the surface of the first substrate, prior to formation of the thin-film transistor on the surface of the first substrate. The interlayer insulator is deposited on the gate electrode. The side wall formation trench is formed in the interlayer insulator, the gate insulator, and the underlayer insulator, running by the channel region of the thin-film transistor and reaching the second light shield layer. Subsequently, the first light shield layer is then deposited, and when the first light shield layer is deposited, the first light shield layer also be formed in the side wall formation trench to form the light shield side wall connected to the second light shield layer in the side wall formation trench.
To resolve the previously described problem, a second electrooptical device of the present invention can include, above a substrate, a pixel electrode, a thin-film transistor connected to the pixel electrode, a wiring connected to the thin-film transistor, and a light shield member three-dimensional covering the thin-film transistor and the wiring.
In the second electrooptical device of the present invention, the thin-film transistor connected to the pixel electrode performs switching control, thereby driving the pixel in an active-matrix driving method. The light shield layer three-dimensionally covers the thin-film transistor. The light shield member prevents light rays entering the substrate vertically or obliquely from above, returning light rays entering the substrate vertically or obliquely from below, and internally reflected light or multiple reflected light in response to these light rays from entering the channel region of the thin-film transistor and the adjacent area of the channel region. The light shield member accurately defines the non-aperture area of each pixel in a grid configuration.
As a result, the second electrooptical device of the present invention increases light tightness, and allows a thin-film transistor with reduced photocurrent leakage to perform correctly switching control on a pixel electrode under severe operational conditions in which high-intensity light and returning light are present. The present invention thus presents a bright and high-contrast image.
In view of such technical effects, the light shield member three-dimensionally covering the thin-film transistor and the wiring, in a narrow sense, can mean a light shield member defining a three-dimensionally closed space which contains the thin-film transistor and the wiring, and in a broader sense, can mean a light shield member defining a three-dimensionally closed space with a slight opening or discontinuity which contains the thin-film transistor and the wiring as long as the light shield member blocks (reflects or absorbs) light coming in three-dimensionally from various directions to some degree.
In another embodiment of the second electrooptical device of this invention, the light shield member can include one light shield layer deposited on the bottom surface and the side wall of a trench formed in the substrate and accommodating the thin-film transistor and the wiring, and another light shield layer covering the trench from above.
In this arrangement, the trench is formed in the substrate, and the one light shield layer is deposited on the bottom surface and the side wall of the trench. The thin-film transistor and the wiring are placed in the trench in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the one light shield layer. Another light shield layer covers the trench from above. With a relatively simple construction and manufacturing process, the thin-film transistor and the wiring are three-dimensionally shielded from light.
In yet another embodiment of the second electrooptical device of the present invention, the light shield member can include a lower light shield layer deposited above the substrate, an upper light shield layer deposited above the thin-film transistor and the wiring, formed on the lower light shield layer, and a side wall light shield layer filling a groove formed from the upper light shield layer to the lower light shield layer outside the thin-film transistor and the wiring in a plan view.
In this embodiment, the thin-film transistor and the wiring are arranged between the lower light shield layer and the upper light shield layer in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the lower light shield layer and the upper light shield layer. The groove can be formed in the interlayer insulator outside the thin-film transistor and the wiring, for example, extending from the upper light shield layer to the lower light shield layer, and the side wall light shield layer fills the trench. With a relatively simple construction and manufacturing process, the thin-film transistor and the wiring are three-dimensionally shielded from light.
In another embodiment of the second electrooptical device of this invention, the light shield member can include in one plane area thereof, one light shield layer deposited on the bottom surface and the side wall of a trench formed in the substrate and accommodating the thin-film transistor and the wiring, and another light shield layer covering the trench from above, and in another plane area, a lower light shield layer deposited on the substrate, an upper light shield layer deposited on the thin-film transistor and the wiring, formed on the lower light shield layer, and a side wall light shield layer filling a groove formed from the upper light shield layer to the lower light shield layer outside the thin-film transistor and the wiring in a plan view.
In this embodiment, a relatively wide trench can be formed in the one plane area, and the one light shield layer is deposited on the bottom surface and the side wall of the trench. The thin-film transistor and the wiring are arranged within the trench in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the one light shield layer. Another light shield layer covers the trench from above. In another area, the thin-film transistor and the wiring are arranged between the lower light shield layer and the upper light shield layer in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the lower light shield layer and the upper light shield layer. A relatively narrow groove is formed in the interlayer insulator outside the thin-film transistor and the wiring, extending from the upper light shield layer to the lower light shield layer, and the side wall light shield layer fills the groove. With a relatively simple construction and manufacturing process, the thin-film transistor and the wiring are reliably three-dimensionally shielded from light. By changing the material of the light shield member from area to area, more flexibility can be provided in device design.
In another embodiment of the second electrooptical device of this invention, the light shield member can include one light shield layer deposited on the bottom surface and the side wall of a trench formed in the substrate and partly accommodating the thin-film transistor and the wiring, an upper light shield layer deposited above the thin-film transistor and the wiring formed above the one light shield layer, and a side wall light shield layer filling a groove formed from the upper light shield layer to the one light shield layer outside the thin-film transistor and the wiring in a plan view.
In this embodiment, a relatively wide trench is formed in the substrate, and the one light shield layer is deposited on the bottom surface and the side wall of the trench, and the thin-film transistor and the wiring are partly accommodated in the trench. The thin-film transistor and the wiring are accommodated in the trench in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the one light shield layer so that a part of the thin-film transistor and the wiring is set to be higher in level than the edge of the trench with respect to the substrate. The upper light shield layer is arranged on the thin-film transistor and the wiring partly accommodated in the trench. A relatively narrow groove is formed from the upper light shield layer to the one light shield layer outside the thin-transistor and the wiring, and the side wall light shield layer fills the groove. With a relatively simple construction and manufacturing process, the thin-film transistor and the wiring are reliably three-dimensionally shielded from light. By fabricating the light shield member of a plurality of light shield layers, more flexibility is provided in device design.
To resolve the above-referenced problem, a third electrooptical device of the present invention can include a pair of first and second substrates with an electrooptical material interposed therebetween, and above the first substrate, a plurality of pixel electrodes arranged two-dimensionally including a first pixel electrode group which is driven in an alternating driving method with a first period and a second pixel electrode group which is driven in an alternating driving method with a second period complimentary to the first period, a thin-film transistor connected to each pixel electrode, a wiring connected to each thin-film transistor, and a light shield member which covers the thin-film transistor and the wiring in a gap area between adjacent pixel electrodes in a plan view and protrudes in a ridge a portion of the gap area between adjacent pixel electrodes of different pixel electrode groups, and further includes above the second substrate, a counter electrode facing the plurality of pixel electrodes.
In accordance with the third electrooptical device of the present invention, the thin-film transistor connected to the pixel electrode performs switching control on the pixel electrode in an active matrix driving method. The first pixel electrode group is driven in an alternating driving method with the first period while the second pixel electrode group is driven in an alternating driving method with the second period which is complementary to the first period. In this way, the electrooptical device may be driven in a scanning line alternating driving method, in which the driving voltage to each pixel is alternated in polarity every scanning line, or may be driven in a data line alternating driving method, in which the driving voltage to each pixel is alternated in polarity every data line, or may be driven in a dot alternating driving method, in which the driving voltage to each pixel is alternated in polarity every pixel. The use of the line alternating driving method serves the purpose of controlling degradation of the electrooptical material caused by the application of a direct current voltage. Furthermore, cross-talk and flickering are also controlled on a presented display image. The light shield layer three-dimensionally covers the thin-film transistor and the wiring in the gap area between the adjacent pixel electrodes. The light shield member prevents light rays entering the substrate vertically or obliquely from above, returning light rays entering the substrate vertically or obliquely from below, and internally reflected light or multiple reflected light in response to these light rays from entering the channel region of the thin-film transistor and the adjacent area of the channel region. The light shield member accurately defines the non-aperture area of each pixel in a grid configuration.
The light shield member protrudes in a ridge a portion of the gap area between adjacent pixel electrodes of different pixel electrode groups. When the electrooptical device is driven in one of the line alternating driving methods, a transverse electric field taking place between the adjacent pixel electrodes of different driving voltage polarities is relatively weakened. If a transverse electric field occurs between the adjacent pixel electrodes in the electrooptical device, which is typically driven by a longitudinal electric field between each pixel electrode and the counter electrode, an operational fault is created in the electrooptical material, such as a orientation defect of the liquid crystal. In accordance with the present invention, the light shield member shortens the distance between the pixel electrode and the counter electrode in the area where such a transverse electric field takes place, thereby intensifying the longitudinal electric field in this area and relatively weakening the adverse effect of the transverse electric field in the same area.
As a result, the third electrooptical device of the present invention increases light tightness and allows a thin-film transistor with reduced photocurrent leakage thereof to perform correctly switching control on the pixel electrode under severe operational conditions in which high-intensity light and returning light are present. The present invention adopts the line alternating driving method, which is effective in lengthening the life of the electrooptical material and reducing flickering. The present invention thus presents a bright and high-contrast image.
In accordance with the third electrooptical device of the present invention, the light shield member includes, in an area between adjacent pixel electrodes of the same pixel electrode group, one light shield layer deposited on the bottom surface and the side wall of a trench formed in the substrate and accommodating the thin-film transistor and the wiring and another light shield layer covering the trench from above. The light shield member also includes, in an area between adjacent pixel electrodes of the different pixel electrode groups, a lower light shield layer deposited on the substrate, an upper light shield layer deposited on the thin-film transistor and the wiring, formed on the lower light shield layer, and a side wall light shield layer filling a groove formed from the upper light shield layer to the lower light shield layer outside the thin-film transistor and the wiring in a plan view.
In this embodiment, a relatively wide trench is formed in the first substrate in the gap area between the pixels where no transverse electric field takes place, and the one light shield layer is deposited on the bottom surface and the side wall of the trench. The thin-film transistor and the wiring are accommodated in the trench in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or are insulated from the one light shield layer. Another light shield layer covers the trench from above. In the gap area between the pixel electrodes where a transverse electric field takes place, the thin-film transistor and the wiring are arranged between the lower light shield layer and the upper light shield layer in a manner that the thin-film transistor and the wiring are insulated from each other with an interlayer insulator interposed therebetween or insulated from the lower and upper light shield layers.
A relatively narrow groove is formed in the interlayer insulator outside the thin-film transistor and the wiring, extending from the upper light shield layer to the lower light shield layer. The side wall light shield layer fills the groove. In the gap area where the transverse electric field takes place, the presence of the light shield member causes the ridge in a localized position, thereby weakening the adverse effect of the transverse electric field. At the same time, in the gap area where no transverse electric field takes place, the presence of the light shield member causes no ridge, thereby reducing the operational fault due to the orientation defect of the liquid crystal, which may be caused by a step at the underlayer beneath the pixel electrode on the first substrate in contact with the electrooptical material.
In another embodiment, a planarizing process is performed on the underlayer beneath the pixel electrode in the area between the adjacent pixel electrodes of the same pixel electrode group.
In this arrangement, the light shield member is arranged in the gap area where no transverse electric field is generated, but the underlayer of the pixel electrode is subjected to the planarizing process. For example, the planarizing process is performed by using a CMP (Chemical Mechanical Polishing) process, or a spin coating process, or by changing the depth of the trench which accommodates the thin-film transistor and the wiring. As a result, in the gap area where no transverse electric field is generated, the operational fault such as the orientation defect of the liquid crystal, which may be caused by a step at the underlayer of the pixel electrode in contact with the electrooptical material, is substantially reduced.
In the second and third electrooptical devices of the present invention, in which the light shield member includes the side wall light shield layer, the upper light shield layer and the lower light shield layer may be integrally formed. In this arrangement, with a relatively simple construction and manufacturing process, a highly reliable light shield layer is formed. After forming the groove in the interlayer insulator which is laminated subsequent to the thin-film transistor or the wiring, the upper light shield layer may fill the groove.
In another embodiment of the second and third electrooptical devices of the present invention, the pixel electrode and the thin-film transistor are connected to each other through a conductive layer having a light shield property. In this embodiment, a contact hole is opened, for example, and light ingress is reliably prevented at the junction point between the pixel electrode and the thin-film transistor, where an internal space enclosed by the light shield member is likely to suffer from light ingress from outside.
In another embodiment of the second and third electrooptical devices of the present invention, the junction point between the pixel electrode and the thin-film transistor is positioned at the center of adjacent thin-film transistors in a plan view. Even if light enters through the junction point, for example the contact hole, between the pixel electrode and the thin-film transistor into the internal space enclosed by the light shield member, the light ingress point is spaced from each thin-film transistor along the surface of the substrate. Accordingly, stray light reaching the channel region of the thin-film transistor and the adjacent area thereof is substantially reduced.
In another embodiment of the second and third electrooptical devices of the present invention, the electrooptical device includes a light shield layer facing the substrate and facing the junction point between the pixel electrode and the thin-film transistor. In this embodiment, a contact hole is opened, for example, and light ingress is reliably prevented at the junction point between the pixel electrode and the thin-film transistor, where an internal space enclosed by the light shield member is likely to suffer from light ingress from outside.
In another embodiment of the second and third electrooptical devices of the present invention, the light shield member can be formed of a film containing a refractory metal. In this embodiment, the light shield member is formed of a single metal layer, an alloy layer, a metal silicide layer, a polysilicide layer, or a multilayer of these layers, each of which layer is fabricated of at least one of the refractory metals such as Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum), Mo (molybdenum), and Pb (lead). The light shield member thus provides high light-shield performance.
In another embodiment of the second and third electrooptical devices of the present invention, the wiring can include scanning lines and data lines intersecting each other, and the light shield member is configured in a grid in a plan view. In this embodiment, the scanning lines and the data lines intersect each other in a grid configuration in an image display area. The light shield member having a grid configuration three-dimensionally covers the grid configuration of the scanning lines and the data lines. This arrangement reduces the possibility that light strays into the thin-film transistors connected to the scanning lines and the data lines through the vicinity of each of the scanning lines and the data lines.
In another embodiment of the second and third electrooptical devices of the present invention, the electrooptical device can further include a storage capacitor formed in a space three-dimensionally covered with the light shield member on the first substrate, and connected to the pixel electrode. In this embodiment, the storage capacitor is formed within a space three-dimensionally enclosed by the light shield member. The storage capacitor prevents light shield performance from dropping while adding a capacitance to the pixel electrode. The voltage holding capability of each pixel electrode is thus increased.
To resolve the previously described object, a projection-type display apparatus can include a light valve including one of the first, second, and third electrooptical devices as mentioned above (and the modifications thereof), a light source for directing light to the light valve, and an optical system for projecting a light beam from the light valve.
In the projection-type display apparatus of the present invention, the light source directs light to the light valve, and the optical system projects a light beam from the light valve to a screen. The light valve can be formed of one of the first, second, and third electrooptical devices. With the above-discussed high lightshield performance, the thin-film transistor with reduced photocurrent leakage thereof reliably performs switching control on the pixel electrode under a high-intensity projection light beam. As a result, the present invention thus presents a bright and high-contrast image.
These operations and other advantages of the present invention will become more apparent from the following discussion of the embodiments.